Conclusion

This study investigated the influence of prenatal methamphetamine exposure on children’s executive functioning at 4 years of age using three performance tasks and a

standardized parental report measure. Children prenatally exposed to methamphetamine were rated as exhibiting more executive function difficulties on the BRIEF-P than controls and showed a trend towards poorer performance on the Day/Night task than controls. Conversely, the methamphetamine-exposed children showed better

performance on the Gift Delay (wrap) task than controls and did not differ from controls on the Bear/Dragon task, although this latter result is probably due to the presence of a ceiling effect.

The BRIEF-P and Day/Night results are consistent with the study hypothesis that prenatal methamphetamine exposure can negatively impact executive functioning at age 4. The subtle nature of the results most likely relates to the presence of background variables in both groups, such as exposure to other neuroactive drugs, which may have masked methamphetamine specific effects. However, studies with larger sample sizes are required to confirm this conjecture. Furthermore, when interpreting the results of this study it is important to acknowledge the potential influence of other maternal lifestyle factors, such as mental illness, on the reported outcomes among the

methamphetamine-exposed group of children. The significance of maternal lifestyle factors on children’s emerging EF skills was highlighted in this study by the negative influence of continued maternal methamphetamine use on child EF performance. Among the experimental group, children with mothers who reported current methamphetamine use performed most poorly on the Day/Night task.

The finding that methamphetamine-exposed children achieved significantly higher performance scores on the Gift Delay (wrap) task, a delay of gratification

paradigm which measures inhibitory control, was unexpected. This result could potentially be explained by differences in parenting practices between the two groups and therefore emphasises the importance of considering ecological variables when interpreting tests of cognitive function.

As a whole, the results of this study are broadly consistent with the hypothesis that prenatal methamphetamine exposure can negatively influence specific aspects of EF and indicate that further research in this area with larger sample sizes is warranted in New Zealand to assess the need for targeted intervention programmes for exposed children and their families. The study also highlights the importance of administering multiple assessments of EF which enable an evaluation of children’s abilities in different life contexts. It is notable that conclusions drawn from this work would have differed greatly if only the BRIEF-P measure or only the Gift Delay (wrap) task had been used to assess executive function among these children.

Finally, it is important to note that although suggestive differences between the methamphetamine-exposed and control children were found in this study, these

differences were relatively subtle. Therefore, with the provision of suitable support for drug-involved families, such as mental health services and parenting skills/early intervention programmes, it is likely that these preschool children would be capable of achieving equivalent outcomes at school to similarly matched peers.

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